Drawing-protractor



E. L. MICHEAU.

DRAWING PROTRACTOR.

APPLICATION FILED APR. 20, 1916. RENEWED DEC. 3. 191

1,342, 129. Patented mm, 924}.

v 2 SHEETS-SHEET-l.

ull- HL.

A -/5 I v InVnlTar E. L. MICHEAU.

DRAWING PROTRACTOR.

APPLICATLON FILED APR. 20, 1916. RENEWED DEC. 3. 1919.

Patented lune 1, 1920.

2 SHEETSSHEET 2.

' His Thar-11255 UNITED STATES PATNT OFFICE.

EDWARD L. MICI-I-EAU, 0F BALTIMORE, MARYLAND.

DnAwinG-P RorRAoron.

Specification of Letters Patent.

Patented June 1, 1920.

Application filed April 20, 1916, Serial Nof92,450. Renewed December 3-, '1919. Serial No. 342,301.

To all whom it may concern."

Be it known that I, EDWARD L. MIGH AU, a resident of Baltimore, in the State of Mary-' land, have invented a new and useful Improvement in Drawing-Protractors,of which the following is a specification.

My present invention relates toprotractors used in drafting which can serve for all kinds of protracting, but is especially depreparation of top osigned for use in the graphic drawings.

The principal objects of my invention are to provide a drawing protractor which is simplein construction, embodying parts so coeperating that any persons understanding the fundamental principles of drafting may bring it into practical use, dispensing with the preliminary directions of an instructor; an instrument of the character described which is inexpensive to manufacture and maintain in good repair; a protractor embodying an annular graduated limb, which may be accurately positioned upon the drawing paper, cloth or board, by aid of a templet, which is removable, permitting the field within the limb to be visible and accessible for placing delineations thereon; and, to provide a scale in combination with said graduated limb which, when the latter is temporarily secured'to the drawing paper, cloth or board, will enable the user to locate various points from a given center, the said scale also serving as a straight-edge embodying a plurality of sets of graduations.

Other objects of the invention will appear in the following detailed description, taken in connection with the accompanying drawing, forming a part of this specification, and

Figure 1 is a plan View of a protractor constructed according to my 1nve11t1on,showing the removable templet in operative relation to the limb. v v

Fig. 2 is a sectional view on the line 22 of Fig. 1.

Fig. 3 is a view similar'to Fig. '1 showing,

the templet removed, and a straight-edge, in operative relation to the limb.

Fig. 4 is a plan view of said straight-edge. Fig. 5 is an elevation of a centering pin. I In the execution of surveys, especially topographic surveys by the stadia method, which forms the basis of engineering work, the relative position of natural and artificial features on the earths surface is determined by an angle measured from a previously laid off baseline to the point to be located, and a 1 distance measured from the point on the base line along the line of the measured plotting the angles and distances contained in topographic survey notes, in the accompanying drawings I have shown the preferred construction of my invention, embodying the following elementsin general:

an annular graduated limb'A; a removable templet B which may be placed in diamet rical alinement within the plane of said limb; a scale or straight-edge C; a centering pin D; and, securing devices E for the limb, such as ordinary thumb tacks. I

Referring first to the limb A which, in the present example, is shown. as of annular shape, providing inner and outer edges 6' and 7, re'spectively, it may have delineated thereon any desired division of graduations 8, only the principal graduations such as 45 degrees, 90 degrees, etc, being shown inthe present example. In order that the limb maybe secured to the drawing board, as by the securing devices or thumb tacks E, it is provided witha plurality of transverse 'per- I forations 9, andfor a purpose to be subsequently' disclosed is preferably provided with recesses 10 formed adjacent diametri cally opposite points; These recesses may be provided by a pair-of lugs 11 disposed in spaced relation and extending inwardly from the edge 6 of the limb,two sets of lugs 11 being provided, as clearly shown in Fig. 8 of the drawing.

As to the templet B, it may be constructed of metal, or of transparent material, such as celluloid or xylonite, and ispreferably of a size to fit within the plane'of the limb A in diametrical alinement with predetermined graduations on the latter. In the example shown, the templet is in alinement with the graduation marks 180 degrees and 360 degrees, a centering delineation 12, such as a line or notch formed in a perforation 13 being equi-distant from the sides and ends of r the templet. In the example shown, the

templet is provided with reduced portions lt fitting into the recesses 10, or, in other words, bounded laterally by the lugs 11 when the templet is in operative relation to the limb: The templet may also be provided 'rwith offsets 15, carried by the reduced porlation to the limb maybe facilitated. The.

tions 14, these offsets resting upon the-lugs 11, so that the protractor may be transported with the templet in operative relation to the limb, without falling, due to the force of gravity, out of such operative position.

QIt is also desirable to provide one or 7 more knobs or, handles 16, which may be mounted uponthe offsets 15, whereby the removal of the templet from operative reperforation 13 is preferably triangular in shape with; its vertex in the longitudinal vided with a longitudinally disposeddeaxis of the templetfenabling the operator tomore accurately place the protractor in operative relation to a given point on the drawing. The templet may also be prolineation l7 parallel to the longitudinal axis, and atransverse.delineation'lS which is at right angles to delineation 17. \Vhen ,the templet is made of transparent material, these delineations should be lowermost or, in other words, on the underside of the templet facilitating alinement with anyh given line or lines on the drawing.

eferr ng now .to the scale or stralghtedge 0, in the present example it isshown provided witha plurality of sets of graduations 19 and 20, the sets differing in the spacing of the graduations. At thestart, or'zero point ofeach set I provide a perforation 21' of a diameterislightly greater than the pointed shank 22 of centering pin D, this perforation being inf alinement with the edge of thejsc'ale to which the graduationslead. 'Each perforation 21 may be in a head 23, as clearly shown in Fig. ft of the drawing. i i

When it .is desired to lay off various angles and distances from a point on a base line, the limb with the templet is positioned in place over the base line so that the delineation l7, or the graduations marked 180 degrees and 360. degrees coincide with the base line on the map, and the centering delineation 121 is directly over the exact point on the baseline. The limb A is then fastened down, as by the thumb tacks E, and the templet B removed. This leaves the plane within the limb accessible for placing delineations' upon the drawing paper, cloth or board, as clearly shown in Fig. 3 of the drawing. The centering pin D isthen positioned with its shank extend 'ing throu'ghthe selected perforation 21 of;

scale C,and also inserted in the baseline point, after which the scale is free to swingin a complete circle "around the center of the pin, as a pivot. By reference to the delineations 8 on the limb, the scale may be placed at any required angle with respect tothe base line, and the distance is scaled tion, an annular graduated plate provided with two pairs of inwardly extending lugs,

and a templet of a size to fit flush with said plate and with its end portions between'the said lugs.

2. A protractor comprising in combination, an annular graduated plate provided with two pairs of inwardly extending lugs, said pairs ,of lugs being disposed at diametrically opposite portions of the plate,

;and a templet of a size sufiicient to flush with the said plate and with its end por-' tions between the said lugs, and provided with a centering delineation equi-distant from its sides and ends. I

8. A protractor comprisingin combination, an annular graduated plate provided with two pairs of inwardly extending lugs, said pairs of lugs being disposed'at diametrically opposite portions "of the plate,

and a templetflof asize to fit flush with' said plate and with its end portionsbetween said lugs, and provided with a sight-opening equi-distant from its sides and ends.

4. A protractor comprising in fcombina tion, an annular graduated plate provided 1105 with two pairs of inwardly extending lugs,

and a templet of a size to fit flush ivith said plate an d with its end'jportions between said lugs, and provided withoffs'ets to rest upon saidlugs.

5. A protractor comprising in combination, an annular graduatedfplate provided with transverse recesses, 1 and a'reinovable templet fitting at opposite ends cesses flush with said plate.

6. A protracto'r comprising in combination, an annular graduated plate provided with transverse recesses," and'a removable templet engaging at opposite ends 'in' the recesses and being ofa sizetofit flush with said plate and in diametricalQalinement with l v rcdetermined graduations of 'the latter. X i

' EDWARD L. Micnnau. l 

